Slip-jointed pile and dolphin construction

ABSTRACT

A marine pile formed by upper and lower lengths of pipe interconnected by a slip-coupling which permits a predetermined amount of axial displacement between these lengths of pipe. This construction has particular application to cluster dolphins of the type wherein the tops of the individual piles are rigidly interconnected.

United States Patent 1191 Holley, Jr.

[ SLIP-JOINTED PILE AND DOLPHIN CONSTRUCTION [76] Inventor: Myle J. Holley, Jr., 1364 Mass Ave.,

Lexington, Mass. 02173 [22] Filed: Mar. 13, 1973 [21] Appl. No.: 340,867

521 U.S.Cl. 61/46, 61/53 1511 Int. Cl E02d 5/22, -E02b 17/00 1581 FieldofSearch 61/46, 53; 114/230, 231;

[5 6] References Cited UNITED STATES PATENTS 3,543,523 12/1970 Nelson 1 71. Amarine pile formed by upper and lower lengths of pipe interconnected by a slip-coupling which permits a predetermined amount of axial displacement between m1 3,834,168 1451 Sept. 10, 1974 3,759,045 9/1973 Nastasic 61/46 FOREIGN PATENTS OR APPLICATIONS 973,405 2/1960 Germany 6l/48 Primary Examiner-Jacob Shapiro Q Att0rney, Agent, .or Firm-R. S. Sciascia; Shrag L 1.

ABSTRACT these lengths of 'pipe. This construction has particular =application to cluster dolphins of the type wherein the ;tops of the individual piles are rigidly interconnected.

" 14 Claims, 3 Drawing Figure SLIP-JOINTED PILE AND DOLPHIN CONSTRUCTION The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

The present invention relates generally to marine pile installations and, more particularly, to a slip-coupled pile construction which may be utilized in marine structures such as cluster dolphin, fender piles and mooring platforms.

One of the inherent problems in the design of marine pile structures involves their inefficient response to loading forces which create a-torque about the piles vertical axis. Thus, for example, in cluster dolphins fabricated with steel pipes, it is difficult to connect these pipes for efficient group resistance to torque so as to, thus, take full advantage of the superior elastic energy absorbing capability of the pipes since most such connections lead to very high pull-out forces usually before significant amounts of this energy can be absorbed. The low and unreliable pull-out capacity of these pipes in the above case, thus, constitutes a serious disadvantage, especially in view of the high cost of repairing a dolphin structure that has experienced partial pull-out.

If a torque-resisting interconnection is used at the top of a cluster dolphin which permits the various individual pipe piles to bend without developing large pull-out forces, considerable difficulty will be encountered in accomplishing the interconnection because of the substantial relative motions among the several pile tops associated with bendingof the individual piles. Any construction which permits such relative motion to occur essentially without restraint will be subject to wear and corrosive effects, and, consequently, will introduce maintenance problems.

There are, therefore, important advantages to be gained by rigidly interconnecting the tops of the individual piles of a cluster dolphin provided this mode of connection can be accomplished without the development of concurrent pile pull-out forces. For example, if the interconnection is achieved by welding or bolting, it can be essentially maintained free. Additionally, such as interconnection will also retain its initial characteristics and permit the various piles to absorb, for example, the entire dolphin torque due to an eccentric breasting load through their individual torsion strengths. The pile bending capability can, therefore, be fully available to resist the applied force as though it were applied without eccentricity and, thus, as though there were no torque.

If the piles of a conventional cluster are rigidly interconnected, however, mooring or breasting forces will produce axial tension forces in some of the outer piles of the dolphin. While it may be possible in some situations to provide adequate resistance to such uplift by, for example, filling the piles with sand or concrete to augment their pull-out resistance, this approach is not always feasible and may be only partially successful.

It is, accordingly, a primary object of the present invention to provide a pile structure wherein torque is successfully resisted and wherein pile pull-out forces are minimized.

Another object of the present invention is provide a slip-coupled pile construction which may be utilized in 2 rigidly interconnected multiple pile dolphins for eliminating partial pile pull-out, except under severe overload conditions.

Another object of the present invention is to provide an improved pile construction for use in cluster dolphins.

Briefly, and in somewhat general terms, the above objects of invention are accomplished by providing each pile of a rigidly interconnected dolphin structure with a slip-coupling which is located at a site remote from the highly corrosive splash zone. Preferably, the slip joint is about half way between the water surface and mud line. The coupling is achieved in the preferred embodiment disclosed by utilizing separate upper and lower cylindrical pile sections of slightly different diameters. With this arrangement, the sections may be telescoped so that their overlapping lengths form a slip zone.

Vertically elongated openings are formed in the outer section at several peripheral locations within this slip zone, and a corresponding number of cooperating lugs are secured to the inner section so as to project through the several openings. This arrangement permits a predetermined amount of relative axial displacement between the two pile sections. The lugs on the inner section serve to transmit torque from inner section to outer section, by bearing on the sides of the elongated openings in the outer section.

On the outside of the inner pile section, a compression stop provides support for the outer pile section during no-load conditions and during pile driving. Thus, although each pile contains two separate pile sections, it can be driven as a single unit and, therefore, no underwater work is required at the slip joint during the installation and/or assembly of the marine structure.

Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings wherein:

. FIG. 1 schematically illustrates a cluster dolphin utilizing the present invention;

FIG. 2 shows the detail of one of the slip-couplings utilized in the various pile members of FIG. 1; and

FIG. 3 is a cross-section through the slip-coupling of FIG. 2 showing the disposition of the various lugs.

Referring now to FIG. 1 of the drawings which schematically illustrates a cluster dolphin which embodies the present invention, it will be seen that the overall structure consists of a suitable multiplicity of embedded, steel pipe piles, such as 1, 2, 3 etc., arranged in an appropriate pattern with their tops rigidly inerconnected by framing 4 to form a unitary structure. The rigid interconnection 4, as noted hereinbefore, is employed to constrain rotation of the cluster of piles about a vertical axis by mobilizing the torsional resistances of the several individual piles to such rotation. With rotation of the cluster thus constrained, the several piles will respond to an eccentric load by bending in essentially the same manner as though the load were concentric. The interconnection of the several piles may use bolting or welding or a combaintion thereof. However the connection is made, it is important that it be rigid.

Each pipe pile consists of an upper section, such as 5, 6, 7 and a lower section, such as 8, 9 and 10, respectively. In the particular modification illustrated, both pile sections are hollow and their diameters are of slightly different size. This size difference allows the section to be telescoped so that their end portions overlap and define a slip zone. in this regard, the inside diameter of the upper section may be larger than the outside diameter of the lower section or vice versa.

Both pile sections are interconnected by a slipcoupling, generally represented by reference characters ll, 12 and l3,which is located at a site removed from the corrosive splash zone. In the modification of FIG. 1, thelocation of this coupling, which, of course, is determined by the length of the lower pile section is selected so as to be approximately midway between the water surface and mud line. Location of the slipcouplings at other elevations is possible but the middepth location is favorable because pile bending moments are small in this region. These slip-couplings, as will be seen hereinafter, permit the various individual upper pile sections to move a predetermined vertical distance with respect to their corresponding lower sections which are embedded in the sea floor.

As will, perhaps, best be seen in FIG. 2, the slipcoupling is accomplished by forming a plurality of relatively narrow longitudinal openings such as 14 and 15 around the lower peripheral rim of upper pile section 5. A like plurality of lugs such as 16 and 17 are welded or otherwise secured to the outer wall surface of lower section 6 at corresponding peripheral locations. Thus, each lug projects through an aperture and, in doing so, effectively interlocks the two sections. These apertures and their close-fitting lugs, as will be understood, permit only axial movement between the two pile sections, and provide for torque transfer from inner to outer pile section. This axial movement is confined to a predetermined distance depending primarily upon the length of the aperture.

Also secured to the outer wall of lower pipe pile 8 of each lower pipe section isa compression stop 19 which may, for example, take the form of a simple shoulder ring welded in place and having a rim thickness sufficient to support the upper pile section. In this connection, in FIG. 2, the upper pile section 5 is shown vertically displaced from its no-load or driving position at which it rests on, and is supported by, compression stop 19. When so supported, each of the lugs will either contact or be in close proximity to the upper ends of the various elongated apertures.

A pair of lateral bearing rings 20 and 22 are also secured to the outside wall of each inner pile section at the top end thereof and a spaced distance therebelow. These bearing rings are included in the assembly to eliminate any binding that might hinder the movement of the unrestrained upper sections in response to applied load forces. The outer surfaces of these rings which come in contact with the inner wall surface of the outer pile section may be treated or otherwise designed to have a low-friction coefficient. The length between these bearing rings is a function of the bearing co-efficient pile pull-out capacity and pile section, and, in a typical installation, this distance may be in the order of 5 to 10 feet.

In assembling these slip-coupled piles, one may first cut out longitudinal slots around the lower rim of the upper pile section. Thereafter, the lower section, having the rings and lugs secured thereto, may be inserted into the upper section with the lugs entering these open ended slots. Then, a stop ring 18 may be welded in place to close these openings. Stop ring 18 additionally strengthens this part of the assembly and prevents any deformation during the driving operation when considerable stresses are developed between it and the shoulder ring.

As shown in FIG. 3, the various lugs, such as 16 and 17, may be spaced by equal angular amounts around the peripheral surface of lower pile 8 and the various longitudinal apertures, such as 14 and 15, similarly spaced around the outer wall surface of upper section 5, with the width of these aperturesjust sufficient to accept each of the lugs. With this relationship. any torsional load can be transferred between the pile sections, and the relative axial movement in the joint may still take place.

It would be pointed out that the compression stop 19 associated with each slip-couple not only provides support for the upper pile section but, additionally, permits the leeward piles to function in compression as well as in bending when the dolphin structure is loaded.

It has been determined that a cluster dolphin with rigidly interconnected pile tops and slip-jointed piles will function essentially in bending as though each pile is simply cantilevered from the seabed during the slip phase, that is during the time the slip-coupling operates in response to an applied load. It will develop almost all of the bending energy associated with simple bending of all the piles, and only very moderate internal forces will develop in the framing during this phase. Additionally, the displacements associated with activation of the slip joints are fully recovered when the dolphin load is removed. After the stop ring contacts the lugs, further overload mobilizes the pull-out capacity of the piles, and causes the piles to function as though rigidly connected in the bending mode. Each pile then acts, not as a simple cantilever, but as a member with bending restraints at top and bottom.

It will be recalled that one of the advantages of the rigid interpile interconnection is that it harnesses the torsional strengths of the individual piles as load absorbing means. However, to achieve this mode of operation, some provision must be made for transmitting pile torque across the slip joint. This is accomplished in the slip-coupling illustrated as a result of the restricted widths of the various apertures which provide only a minimum of clearance for the lugs projecting therethrough. It would also be pointed out that whenever the piles utilized in the dolphins are hollow steel pipes for example, these pipes may be filled with sand or concrete below the slip joint to enhance the total load capacity of the dolphin. It is, likewise, possible to fill the piles above the slip joints to further increase this capacity. Such upper filling would have the effect of delaying the initiation of the pile slip mode, that is, it would stiffen the dolphin by delaying action of the slip joints until the imposition of a minimum load.

What is claimed is:

1. A pile construction for use in a marine structure comprising,

an upper length of pipe;

a lower length of pipe,

said lengths of pipe having different diameters; and

means interconnecting said lengths of pipe such that a predetennined amount of axial displacement can take place between said lengths of pipe,

said interconnecting means also permitting torque transfer between said lengths of pipe.

2. In a pile construction as defined in claim 1,

means secured to said lower length of pipe for supporting said upper length of pipe such that end portions thereof are telescoped and form an overlap zone.

3. A pile construction for use in a cluster dolphin of the type wherein the top portions of the individual pil ings are rigidly interconnected comprising,

an upper length of pipe;

a lower length of pipe, said lengths of pipe having different diameters;

means secured to said lower lengths of pipe for supporting said upper lengths of pipe such that end portions of said lengths of pipe telescope to form an overlap zone;

a plurality of elongated apertures formed in one said lengths of pipe around the peripheral surface thereof at locations that are within said overlap zone; and

a like plurality of lugs secured to the other lengths of pipe at corresponding peripheral locations that are within said overlap zone such that each lug projects through an elongated aperture, said apertures and lugs forming a slip-coupling which interlocks said lengths of pipe so as to prevent relative rotation therebetween while permitting a predetermined amount of axial displacement therebetween.

4. In an arrangement as defined in claim 3,

wherein the width of each elongated aperture and the width of each lug are substantially equal whereby torsional forces may be transmitted across said slipcoupling without any substantial relative rotation between said lengths of pipe.

5. In an arrangement as defined in claim 3 wherein said means for supporting said upper length of pipe consists of an external collar secured to said lower length of pipe with said upper length of pipe resting thereon.

6. A cluster dolphin comprising, in combination,

a plurality of pipe piles arranged in a preselected pattern with their lower ends embedded into the sea floor, and their upper ends rigidly interconnected to form a unitary structure, each of said pipe piles comprising a separate lower and upper section, with said sections being interconnected such that a predetermined amount of relative axial displacement can take place therebetween.

7. A dolphin structure comprising,

a plurality of pilings,

each piling consisting of an upper and lower tubular section with end portions of said sections being telescoped to form an overlap zone;

a slip-coupling fabricated within each overlap zone and interconnecting said upper and lower sections,

said slip-coupling permitting a predetermined amount of displacement between said upper and lower sections along the longitudinal axis of said sections; and means for rigidly interconnecting the top ends of the upper tubular sections of said plurality of pilings so as to form a unitary structure,

- a plurality of pipe piles embedded in the ocean floor in a predetermined arrangement, each pipe pile consisting of separate upper and lower lengths of pile; means interconnecting said lengths such that relative longitudinal displacement of a predetermined amount can take place therebetween; and means rigidly interconnecting the top ends of said upper lengths, whereby whenever the lower ends of said lower lengths are embedded in the sea floor and aload directed against said dolphin, the top portion thereof may initially experience displacement and bending to absorb said load without developing significant pull-out forces in said piles. 10. A cluster dolphin comprising, in combination, a plurality of pipe piles embedded in the ocean floor in a preselected pattern; each of said pipe piles consisting of an upper length of pipe and a lower length of pipe, said lengths of pipe having different diameters; means interconnecting said lengths of pipe such that a predetermined amount of axial displacement can take place between said lengths, said interconnecting means being such that torsional forces can be coupled between said lengths of pipe; and means rigidly interconnecting the upper ends of said plurality of pipe piles to form a unitary structure.

11. In an arrangement as defined in claim 10,

wherein said interconnecting means is such that after said predetermined amount of axial displacement occurs, said upper and lower lengths of pipe are interlocked against further relative axial displacement.

12. In an arrangement as defined in claim 10,

means for supporting said upper length of pipe such that an end portion of this length of pipe and said upper length of pipe are telescoped to form an overlap zone.

13. In an arrangement as defined in claim 10,

wherein said means for interconnecting said lengths of pipe and said means for supporting said upper length of pipe are such that said lengths of pipe may be driven into the sea floor as a unitary structure.

14. A cluster dolphin comprising in combination a plurality of pipe piles arranged in a pre-selected pattern with their lower ends embedded into the sea floor, each of said pipe piles comprising a separate lower and upper section;

means rigidly interconnecting the upper ends of the upper sections to form a unitary structure; and

3,834,168 7 8 means interconnecting the upper and lower sections sional transfer can take place between said sections of each pile such that only a predetermined amount of relative axial displacement can occur between said sections and such that any relative rotation cannot occur between said sections whereby torwhenever an eccentric lateral load is applied to one or more of said piles. 

1. A pile construction for use in a marine structure comprising, an upper length of pipe; a lower length of pipe, said lengths of pipe having different diameters; and means interconnecting said lengths of pipe such that a predetermined amount of axial displacement can take place between said lengths of pipe, said interconnecting means also permitting torque transfer between said lengths of pipe.
 2. In a pile construction as defined in claim 1, means secured to said lower length of pipe for supporting said upper length of pipe such that end portions thereof are telescoped and form an overlap zone.
 3. A pile construction for use in a cluster dolphin of the type wherein the top portions of the individual pilings are rigidly interconnected comprising, an upper length of pipe; a lower length of pipe, said lengths of pipe having different diameters; means secured to said lower lengths of pipe for supporting said upper lengths of pipe such that end portions of said lengths of pipe telescope to form an overlap zone; a plurality of elongated apertures formed in one of said lengths of pipe around the peripheral surface thereof at locations that are within said overlap zone; and a like plurality of lugs secured to the other lengths of pipe at corresponding peripheral locations that are within said overlap zone such that each lug projects through an elongated aperture, said apertures and lugs forming a slip-coupling which interlocks said lengths of pipe so as to prevent relative rotation therebetween while permitting a predetermined amount of axial displacement therebetween.
 4. In an arrangement as defined in claim 3, wherein the width of each elongated aperture and the width of each lug are substantially equal whereby torsional forces may be transmitted across said slip-coupling without any substantial relative rotation betweEn said lengths of pipe.
 5. In an arrangement as defined in claim 3 wherein said means for supporting said upper length of pipe consists of an external collar secured to said lower length of pipe with said upper length of pipe resting thereon.
 6. A cluster dolphin comprising, in combination, a plurality of pipe piles arranged in a preselected pattern with their lower ends embedded into the sea floor, and their upper ends rigidly interconnected to form a unitary structure, each of said pipe piles comprising a separate lower and upper section, with said sections being interconnected such that a predetermined amount of relative axial displacement can take place therebetween.
 7. A dolphin structure comprising, a plurality of pilings, each piling consisting of an upper and lower tubular section with end portions of said sections being telescoped to form an overlap zone; a slip-coupling fabricated within each overlap zone and interconnecting said upper and lower sections, said slip-coupling permitting a predetermined amount of displacement between said upper and lower sections along the longitudinal axis of said sections; and means for rigidly interconnecting the top ends of the upper tubular sections of said plurality of pilings so as to form a unitary structure, whereby whenever the lower ends of said lower tubular sections are embedded in the sea floor and a loading force is directed against said dolphin, the flexural behavior of each pile is essentially simple cantilever bending before any pull-out forces are applied to the lower part of the dolphin.
 8. In an arrangement as defined in claim 7, wherein said slip-coupling is located approximately midway between the water surface and the mud line.
 9. A cluster dolphin comprising, in combination, a plurality of pipe piles embedded in the ocean floor in a predetermined arrangement, each pipe pile consisting of separate upper and lower lengths of pile; means interconnecting said lengths such that relative longitudinal displacement of a predetermined amount can take place therebetween; and means rigidly interconnecting the top ends of said upper lengths, whereby whenever the lower ends of said lower lengths are embedded in the sea floor and a load directed against said dolphin, the top portion thereof may initially experience displacement and bending to absorb said load without developing significant pull-out forces in said piles.
 10. A cluster dolphin comprising, in combination, a plurality of pipe piles embedded in the ocean floor in a preselected pattern; each of said pipe piles consisting of an upper length of pipe and a lower length of pipe, said lengths of pipe having different diameters; means interconnecting said lengths of pipe such that a predetermined amount of axial displacement can take place between said lengths, said interconnecting means being such that torsional forces can be coupled between said lengths of pipe; and means rigidly interconnecting the upper ends of said plurality of pipe piles to form a unitary structure.
 11. In an arrangement as defined in claim 10, wherein said interconnecting means is such that after said predetermined amount of axial displacement occurs, said upper and lower lengths of pipe are interlocked against further relative axial displacement.
 12. In an arrangement as defined in claim 10, means for supporting said upper length of pipe such that an end portion of this length of pipe and said upper length of pipe are telescoped to form an overlap zone.
 13. In an arrangement as defined in claim 10, wherein said means for interconnecting said lengths of pipe and said means for supporting said upper length of pipe are such that said lengths of pipe may be driven into the sea floor as a unitary structure.
 14. A cluster dolphin comprising in combination a plurality of pipe piles arranged in a pre-selected pattern with their lower ends embedded into the sea floor, each of said pipe piles comprising a separate lower and upper section; means rigidly interconnecting the upper ends of the upper sections to form a unitary structure; and means interconnecting the upper and lower sections of each pile such that only a predetermined amount of relative axial displacement can occur between said sections and such that any relative rotation cannot occur between said sections whereby torsional transfer can take place between said sections whenever an eccentric lateral load is applied to one or more of said piles. 